The inspectors withdrew after an Iraqi official demanded that they first provide a written declaration of what they were looking for, the official Iraqi News Agency said.

"This was an absolutely legal, no-notice inspection and they blocked us," Richard Butler, head of the U.N. Special Commission that oversees inspections, told The Associated Press in New York.

Later Wednesday, however, an Iraqi official suggested the standoff occurred because of a mistake by an Iraqi escort in declaring the site sensitive.

The incident - which has the potential to blow up into another U.N.-Iraq crisis - came two days after Butler announced that he was ordering the resumption of surprise inspections. On Tuesday, the inspectors visited 32 sites and on Wednesday, 10 more.

Butler said the Iraqi demand for a written notice was "simply wrong" and "nonsense."

Despite the Iraqi interference, Butler plans to continue the searches, which are expected to conclude by early next week, said U.N. spokesman Fred Eckhard.

Secretary of State Madeleine Albright, speaking at a NATO meeting in Brussels, Belgium, said Iraq had no choice but to work with the inspectors as it has pledged to do.

"There will be no comprehensive review (of sanctions against Iraq) until it is evident that Iraq is cooperating with UNSCOM," she said, using the acronym for the weapons team.

Unannounced visits in the past have been a major source of friction with Iraq, leading to three crises in the past year.

Iraq had suspended the inspections in August. It allowed them to resume only last month, averting a military strike by the United States and Britain. The two countries have left an armada in the Persian Gulf to ensure that Iraq abides by its promise to cooperate.

Still, Wednesday's dispute elicited a cautious reaction from the United States.

David Leavy, spokesman for the National Security Council, said Iraq's rebuff to inspectors did not bring the United States closer to armed conflict with Iraq. He stressed that President Clinton's administration wants to hear Butler's report to the Security Council on an overall assessment of Iraq's compliance - not just on inspections but also in turning over documents.

UNSCOM must certify that Iraq has eliminated its chemical, biological and nuclear weapons as well as long-range missiles before U.N. economic sanctions can be lifted. The sanctions were imposed after Iraq's 1990 invasion of Kuwait. Iraqi officials have long insisted they have eliminated all illegal weapons.

In New York, Iraq's Deputy U.N. Ambassador Saeed Hasan said the building in dispute was the headquarters of the Baghdad branch of the Baath Party.

Oil Minister Amer Mohammed Rashid said the U.N. team arrived Wednesday morning at the site, which their Iraqi escort declared as "sensitive."

The escort allowed four inspectors to enter briefly, Rashid said. They came out and requested 12 inspectors be allowed to enter. "This was refused by the Iraqi (escort)," he said.

Rashid added that the escort was wrong in declaring the site sensitive, which he said would include installations of the elite Republican Guard and security services.

The minister told a news conference, however, that the inspectors are deliberately seeking a confrontation.

He said Iraq did agree in a Feb. 23 agreement with U.N. Secretary-General Kofi Annan to allow surprise inspections. But, he said, the United Nations also agreed "to respect the security, integrity and legitimate concerns of the Iraqi government," which Rashid said included prior notice in visiting sites the government considered sensitive.

U.N. inspectors have insisted that their searches should not be restricted by Iraq in any way.

"The practices of the inspectors ... have the clear goal of creating crises and problems," the Iraqi News Agency quoted Gen. Hossam Mohammed Amin as saying.

As many as 140 inspectors were working in Iraq on Wednesday, as well as some visiting experts, said Caroline Cross, a U.N. spokeswoman in Baghdad. She would not give the exact number involved but said it was "a little less than 200."

Inspectors used helicopters in one of the searches Wednesday outside Baghdad, Amin said.

A team from the International Atomic Energy Agency, which is responsible for inspecting Iraq's nuclear programs, also arrived in Baghdad on Wednesday and met with Iraqi officials, said Gen. Hossam Mohammed Amin, who heads an office that works with UNSCOM.